295/30R20 vs 255/40R20
255/40R20 is outside the ±3% rule as a replacement for 295/30R20: the diameter differs by +3.94%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 255/40R20 on a car calibrated for 295/30R20, the speedometer reads 57.7 mph when you're really doing 60, and the odometer under-counts by 3.9%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.2 mph |
| 45 mph | 46.8 mph |
| 60 mph | 62.4 mph |
| 70 mph | 72.8 mph |
| 80 mph | 83.2 mph |
Other sizes close to 295/30R20
- 295/30R20 vs 245/40R19-0.93%
- 295/30R20 vs 255/40R19+0.23%
- 295/30R20 vs 245/40R20+2.77%
- 295/30R20 vs 245/35R20-0.80%
- 295/30R20 vs 255/35R20+0.22%
- 295/30R20 vs 275/35R20+2.26%
- 295/30R20 vs 225/45R19+0.01%
- 295/30R20 vs 285/35R19-0.42%
- 295/30R20 vs 285/35R20+3.28%
- 295/30R20 vs 285/30R20-0.88%
- 295/30R20 vs 275/30R20-1.75%
- 295/30R20 vs 265/35R20+1.24%
Questions
Can I replace 295/30R20 with 255/40R20?
255/40R20 is outside the ±3% rule as a replacement for 295/30R20: the diameter differs by +3.94%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 295/30R20 and 255/40R20?
255/40R20 is 1.06" taller and 40 mm narrower; the sidewall is +0.53". At an indicated 60 mph you'd actually be doing 62.4 mph.
Will 255/40R20 fit on 295/30R20 wheels?
Both use a 20" rim, so the wheel diameter matches; check the wheel's width range for a 255 mm tire and the fender clearance.